What is the problem you are trying to solve? If it is only spamming, how about a probation period before new accounts can post? No further hurdles than that. The most recent post is from 40 minutes ago, posted by a 42-minute-old account. For a spammer, having to create an account with a password and store those credentials and come back a week later to post is far more troublesome than the current instant gratification.
Surprising we don't have that yet. If we add this - which sounds like a great idea - there should be a landing page for the newcomers saying something like this:Hey, look, nobody likes spammers, so we added a waiting period. You can still browse, just not post or comment for this long. After that, you're welcome to introduce yourself to the hubskifolk! Just use #newtohubski as one of your tags!